My husband wants to spend the day away from me

One of my husband's childhood friends is coming to our city to visit for 3 days. On the first day (today) my husband invited him to dinner here at home. I tidied up the whole house and made a great dinner, and my husband thanked me when his friend left. Then just told me that he's going out to take his friend to a museum and on a tour tomorrow all day until 4 pm, and he canceled all his meetings and work commitments on Wednesday to spend the whole day with his friend, telling me he will return late at night on Wednesday.

Am I being selfish to think that my husband never “cleared his day” to be with me? and when I asked what “we” were going to do, my husband was straight with me saying that I wasn't invited, that he wanted to spend this time alone with his friend and remember the old times.

When I told him I was upset about being purposely left out, he said I could go out with them to the museum on Tuesday morning, but that's it, the rest of Tuesday and Wednesday all day he prefers to be alone with the friend (He clearly said that they want to feel comfortable talking about their childhood and adolescence without anyone getting in the way and that it will be more fun without me, that I’m being controlling).

I feel so stupid that he thinks it's okay to choose when he wants my company and when I should just disappear. Am I being selfish?

Ps- to be clear, I know my husband and really don’t think they want to do something unfaithful or bad, he just really doesn’t want me there :/